Enforcing SSL (https) for a Joomla! page.
In Joomla! 1.5 you can enable SSL on any page that has a menu link (or displays under any menu link as in an article arrived at by clicking in a category or section list).
In the backend (/administrator) go to the menu manager and open up any link to a page you want to be on https://. On the right side, click to open System parameters. Select yes in SSL enabled.
This method may not work in every server environment. If you are using a shared certificate with another address than your domain address, it may not work.